Gallstones are a common problem in the United States and the most frequent cause of gallbladder inflammation. Calculi in other parts of the biliary system are also common place as are calculi in the urinary system. Several percutaneous and open surgical procedures are available for removing calculi from the biliary or the urinary system. With respect to the biliary system, one invasive, open surgical procedure is the cholecystectomy in which the gallbladder is removed along with stones from the cystic and common ducts. A T tube is commonly inserted in the common duct for removal of residual calculi. However, such invasive, open surgical procedures are subject to an extensive recovery period lasting from two to six weeks.
Minimally invasive surgical procedures that utilize a percutaneous access include a percutaneous cholecystolithotomy in which calculi are removed through a percutaneously inserted access sheath. Several postoperative access routes such as a transcholedochal, a transcystic duct, a transcholecystic for gallbladder stones and a transcholecystic for choledochal stones are employed for removing biliary stones from the gallbladder, cystic duct, or common duct. In such cases, the extractions are carried out through the fistula tract left by a T tube. The percutaneous extraction is based on the use of forceps or basket-tipped catheters. Forceps enable a quick extraction of stones within reach. Furthermore, forceps facilitate extracting compacted stones. However, forceps are best suited in conjunction with endoscopes to avoid inadvertent extraction of intact mucosa. Another problem with forceps is that they cannot negotiate double or triple curves or the exaggerated tortuosities of fistula tracks. This problem is partially overcome with the basket-tipped catheter which can traverse such winding courses, but it is frequently not possible to seize impacted stones.
A problem with a basket-tipped catheter arises in the case of very small or flat stones particularly when they lie in large cavities where they have ample room for displacement. Most stone extraction baskets are of the helically-shaped variety which permit entry of the stone only from the side of the basket. This is due typically to the tip of the basket, which usually contains a small length of cannula for holding the ends of the wire basket together. Thus, a head-on or an open-ended approach is not possible with these "leading tip" stone retrieval baskets. Helically-shaped baskets also have a tendency to fold on themselves rather to open when pushed against a wall of a hollow organ such as a gallbladder. This reduces the chance of capturing stones. In addition, the relatively sharp tip of such baskets tends to cause an indentation and possible injury of the organ wall.
With presently available open-ended baskets in which the wires of the basket form an open loop to provide a head-on approach, the basket wire is comprised of stainless steel, which is subject to kinking and does not have the desired resiliency for more than one stone capture.